Spray cooling thermal management system and method for semiconductor probing, diagnostics, and failure analysis

ABSTRACT

A micro-spray cooling system beneficial for use in testers of electrically stimulated integrated circuit chips is disclosed. The system includes micro-spray heads disposed about a probe head. The spray heads and probe head are disposed in a sealed manner inside a spray chamber that, during operation, is urged in a sealing manner onto a sealing plate holding the integrated circuit under test. The atomized mist cools the integrated circuit and then condenses on the spray chamber wall. The condensed fluid is pumped out of the chamber and is circulated in a chiller, so as to be re-circulated and injected again into the micro-spray heads. The pressure inside the spray chamber may be controlled to provide a desired boiling point.

This Application is a Divisional of, and claims priority from, U.S.application Ser. No. 12/402,475, filed on Mar. 11, 2009, which is aDivisional of U.S. application Ser. No. 11/205,898, filed on Aug. 16,2005, which is a Divisional of U.S. application Ser. No. 10/222,107,filed Aug. 16, 2002, and the entire disclosures of which are relied uponand incorporated herein be reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system and a method for thermalmanagement of an electrically stimulated semiconductor integratedcircuit undergoing probing, diagnostics, or failure analysis.

2. Description of the Related Art

Integrated circuits (ICs) are being used in increasing numbers ofconsumer devices, apart from the well-known personal computer itself.Examples include automobiles, communication devices, and smart homes(dishwashers, furnaces, refrigerators, etc.). This widespread adoptionhas also resulted in ever larger numbers of ICs being manufactured eachyear. With increased IC production comes the possibility of increased ICfailure, as well as the need for fast and accurate chip probing, debug,and failure analysis technologies. The primary purpose of today'sprobing, debug, and failure analysis systems is to characterize thegate-level performance of the chip under evaluation, and to identify thelocation and cause of any operational faults.

In the past, mechanical probes were used to quantify the electricalswitching activity. Due to the extremely high circuit densities, speeds,and complexities of today's chips, including the use of flip-chiptechnology, it is now physically impossible to probe the chipsmechanically without destructively disassembling them. Thus, it is nownecessary to use non-invasive probing techniques for chip diagnostics.Such techniques involve, for example, laser-based approaches to measurethe electric fields in silicon, or optically-based techniques thatdetect weak light pulses that are emitted from switching devices, e.g.,field-effect transistors (FETs), during switching. Examples of typicalmicroscopes for such investigations are described in, for example, U.S.Pat. Nos. 4,680,635; 4,811,090; 5,475,316; 5,940,545 and Analysis ofProduct Hot Electron Problems by Gated Emission Microscope, Khurana etal., IEEE/IRPS (1986), which are incorporated herein by reference.

During chip testing, the chip is typically exercised at relatively highspeeds by a tester or other stimulating circuit. Such activity resultsin considerable heat generation. When the device is encapsulated and isoperated in its normal environment, various mechanisms are provided toassist in heat dissipation. For example, metallic fins are oftenattached to the IC, and cooling fans are provided to enhance air flowover the IC. However, when the device is under test, the device is notencapsulated and, typically, its substrate is thinned down for testingpurposes. Consequently, no means for heat dissipation are available andthe device under test (DUT) may operate under excessive heat so as todistort the tests, and may ultimately fail prematurely. Therefore, thereis a need for effective thermal management of the DUT.

One prior art system used to cool the DUT is depicted in FIG. 1. Thecooling device 100 consists of a cooling plate 110 having a window 135to enable optical probing of the DUT. The window 135 may be a simple cutout, or may be made of thermally conductive transparent material, suchas synthetic diamond. The use of synthetic diamond to enhance cooling isdescribed in, for example, U.S. Pat. No. 5,070,040, which isincorporated herein by reference. Conduits 120 are affixed to thecooling plate 110 for circulation of cooling liquid. Alternatively, theconduits may be formed as an integral part of the plate.

FIG. 1 depicts in broken line a microscope objective 105 used for theoptical inspection, and situated in alignment with the window 135.During testing, the cooling plate is placed on the exposed surface ofthe DUT 160, with the window 135 placed over the location of interest.Heat from the device is conducted by the cooling plate to the conduitsand the cooling liquid. The cooling liquid is then made to circulatethrough a liquid temperature conditioning system, such as a chiller,thereby removing the heat from the device. Typically, however, the DUTincludes auxiliary devices 165, which limit the available motion of thecooling plate, thereby limiting the area available for probing Toovercome this, custom plates are made for specific devices, leading toincreased cost and complexity of operation of the tester.

There is a need for an innovative, inexpensive, flexible, and thermallyeffective thermal management solution for chip testers or probers.

SUMMARY OF THE INVENTION

The present invention provides a mechanism for removing heat from a DUT,thereby allowing for inspection of the device under electricalstimulation. Therefore, the system is particularly adaptable for usewith optical microscopes used for probing, diagnostics and failureanalysis of the DUT.

In one aspect of the invention, a thermal management system is providedwhich utilizes an atomized liquid spray for removing heat from the DUT.A spray head is provided about an objective lens housing, and thisarrangement is placed inside a spray chamber. The spray chamber issealed to a plate upon which the DUT is situated. The pressure insidethe chamber may be controlled to obtain the proper evaporation of thesprayed liquid. Pressure transducers and temperature sensors may beinstalled on the pressure chamber to monitor the operation of thethermal management system.

In another aspect of the invention, the spray cooling is accomplishedusing several banks of atomizers. According to one implementation, allof the atomizers are commonly connected to one liquid supply. On theother hand, according to other implementations, liquid delivery to each,or to groups, of atomizers may be controlled separately so as to varythe pressure, the timing, and/or the type of liquid delivered to variousatomizers.

In a further aspect of the invention, control instrumentation isprovided for accurate operation of the thermal management system. TheDUT temperature can be controlled via coolant temperature, coolant flowrate (directly tied to coolant delivery pressure), and coolant boilingpoint (a function of spray chamber pressure and vapor temperature. Notethat at its saturation temperature, the temperature of the saturationliquid is the same as its vapor (non-superheated). A temperature sensorclose to the coolant delivery point monitors the coolant deliverytemperature, which is fed back to the thermal management system'scontroller. The controller controls the liquid temperature conditioningsystem, which may be a chiller or other device to control the coolant'stemperature to a pre-determined value. Such systems are well known tothose skilled in the art.

Spray chamber pressure is measured with a pressure transducer incommunication with the spray chamber. Vapor temperature (measured with atemperature sensor in communication with the spray chamber) and spraychamber pressure determine the coolant's boiling point, which in turninfluences the manner in which the DUT temperature is controlled. Thespray chamber pressure can be manipulated to influence the coolant'sboiling point. The spray chamber pressure may be affected, for example,by a solenoid valve in communication with the spray chamber, byadjusting the return pump's speed, or by manipulating the pressureinside the liquid temperature conditioning system's reservoir. Amechanical pressure relief valve provides a safety release in the eventthat the solenoid valve fails.

One or more of the afore-mentioned approaches, individually or incombination, may be used to control the coolant flow rate and/or thecoolant's boiling point. The ultimate goal is to use the instrumentationto control the DUT to a predetermined temperature. The temperature ofthe DUT may be measured by mechanical contact with a thermocouple orother sensor, by non-contact means such as a thermal imaging camera, orby any other means suitably accurate for the intended temperaturestability. Any means for measuring the DUT temperature may be employedin the control of the DUT temperature. The specific examples given hereare meant for illustrative purposes only and are not meant to limit thisinvention in any way.

A computer or other electronic or mechanical control system may be usedto monitor DUT temperature and provide the necessary adjustment ofspray. For example, if the DUT temperature rises, the computer couldincrease the flow rate, decrease the fluid temperature, or both.

In a further aspect of the invention, a solid immersion lens (SIL) isused in combination with the objective lens. SILs are well known tothose skilled in the art and are included here by reference. The SILenables transmission of optical energy between the DUT and the objectivelens regardless of the type and manner of cooling spray used. Thus, theatomizers and the fluid pressure can be selected freely for optimal heatremoval efficiency. For example, the size, design/style, density, angle,and number of atomizers can all be adjusted. In addition, thetemperature and type of coolant used can also be adjusted.

In a further aspect of the invention, a DUT retention frame is providedwith a seal plate that enables sealing contact with a spray chamber. Insome arrangements, the seal plate is provided with o-rings preventingcooling fluid from reaching the pin side of the DUT. One possibleadvantage of the arrangement is that non-dielectric coolants such aswater can be used because the coolant does not come in contact with theelectrically exposed (front) side of the chip. In other arrangements,the seal plate may have cooling channels provided therein to enablecooling (with dielectric coolants) of the DUT from the pin side, i.e.,back side cooling. In yet other arrangements, the DUT retention frameand seal plate may be integrated into an integrated seal plate. Onepossible advantage of this is that the backside cooling channel can beisolated from the spray side of the DUT. This allows separate coolingsystems to be implemented, including the possible use of two differentcoolants.

In yet a further aspect of the invention, the SIL is in contact with athermally conductive cover plate which is transparent to the NIR andcompatible with the SIL optical design. For example, the cover plate maybe made of silicon, sapphire, or diamond. The walls of the chamber aresealed to the cover plate. The cover plate is placed in contact with theDUT and the surface of the window inside the chamber is cooled by thespray mechanism previously described. This aspect may have the advantagethat the heat from the DUT is spread out before being extracted by thespray cooling, and that the spray is completely enclosed, avoidingunnecessarily cooling areas around the DUT.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described herein with reference to particularembodiments thereof which are exemplified in the drawings. It should beunderstood, however, that the various embodiments depicted in thedrawings are only exemplary and may not limit the invention as definedin the appended claims.

FIG. 1 depicts a plate cooling system according to the prior art.

FIG. 2 depicts an embodiment of the inventive cooling system in anexploded view.

FIG. 3 depicts a cross section schematic of an embodiment of theinventive cooling system.

FIG. 4 depicts an embodiment of the inventive cooling system using asolid immersion lens.

FIG. 5 is a cross section schematic of a DUT holder arrangementaccording to an embodiment of the inventive cooling system allowing theuse of non-dielectric fluids such as water.

FIG. 6 is a cross section schematic of a DUT holder arrangementaccording to another embodiment of the inventive cooling system allowingadditional cooling of the DUT through the pin side.

FIG. 7 depicts a cross section schematic of an embodiment of theinventive cooling system.

FIG. 8 is a cross section schematic of a DUT holder arrangement withseparate DUT retention frame and seal plate.

FIG. 9 is a cross section schematic of a DUT holder arrangement withintegrated DUT retention frame and seal plate and employing independentbackside cooling.

FIG. 10 is a cross section schematic of a DUT holder arrangement withintegrated DUT retention frame and seal plate and employing backsidecooling.

DETAILED DESCRIPTION

Various embodiments and implementations of the present invention can beused in conjunction with various IC testers and probers, so as toprovide cooling of an IC that is electrically stimulated. In one generalaspect, an atomized liquid spray is provided about a probe head so as tocool the DUT as the probe head collects data. Any probe head may beused, for example, the probe head may be in the form of an opticalphoton-counting time-resolved receiver, optical emission microscope, orlaser-based probing tool. In order to provide a more detailedexplanation of various aspects and features of the invention, theinvention will be described with reference to more specific IC probers,i.e., optical photon-counting time-resolved emission probers. However,it should be appreciated that such detailed description is provided onlyas an example and not by way of limitation.

FIG. 2 depicts an exploded view of one embodiment of the inventivecooling system. The cooling system depicted in FIG. 2 may be used withany type of microscope used for inspection and/or testing of ICs. Forclarity, FIG. 2 shows only the objective lens portion opticalinspection/probing system, except for the parts relating to its coolingsystem. As shown in FIG. 2, a retention frame 270 holds the DUT 260 ontoseal plate 280. The seal plate is mounted to a load board, which in turnis connected to a conventional test head (not shown) of a conventionalautomated testing equipment (ATE). The ATE sends stimulating signals tothe DUT 260, to simulate operating conditions of the DUT 260. This isdone conventionally using the load board with an appropriate socket forthe DUT.

An objective housing 205 houses the objective lens of the testingsystem. The housing 205 and objective lens generally form an opticalreceiver of the system, i.e., the probe head. The housing 205 is mountedalong with a spray head 210 having atomizers 215 provided therein. Thisentire assembly is situated inside spray chamber 225, having a seal 230affixed to its upper surface. The seal 230 may be sliding or otherwise.The spray chamber 225 is affixed to a translation stage, e.g., an x-y-zstage (not shown). To perform testing in an embodiment employing thesliding seal, the spray chamber 225 is brought in contact with thesealing plate 280, so that sliding seal 230 creates a seal with thesealing plate 280. The seal may be hermetic, but a hermetic seal is notrequired. In this manner, the spray chamber 225 may be moved about so asto bring the objective lens into registration with the particular areaof the DUT sought to be imaged, without breaking the seal with thesealing plate 280.

In another embodiment, the housing 225 is connected to the sealing plate280 through a flexible bellows (not shown). The bellows material shouldbe compatible with the coolant temperature and chemical properties. Somepotential materials include folded thin-walled steel and rubber.

During testing, fluid is supplied to the atomizers 215 via coolantsupply manifold 255. The boiling point of the coolant can be controlledby controlling the pressure inside the spray chamber 225 using solenoid220, or otherwise. In one implementation of the invention, the pressureinside the spray chamber 225 is measured using pressure transducer 250and of that of the coolant supply is measured using pressure transducer240, while the temperature of the cooling fluid is measured withtemperature sensor 241 and of the spray is measured using temperaturesensor 245. As a safety measure, a mechanical pressure relief valve 235is optionally provided.

The coolant delivery pressure is measured by a pressure transducer closeto the coolant delivery point 240. The spray chamber pressure is alsomeasured by another pressure transducer 250. For fixed or varyingcoolant temperature and spray chamber pressure, the measured coolantdelivery pressure is fed back to the controller to ensure adequatecoolant delivery pressure for a required DUT temperature. The flow rate,and thus the cooling rate, can be controlled by the coolant deliverypressure.

FIG. 3 is a cross-sectional schematic of the spray cooling systemaccording to an embodiment of the present invention. Specifically, DUT360 is attached to seal plate 370, which is then mounted to the DUT loadboard (not shown). The described assembly is affixed to the load board,which is connected to a test adapter in a conventional manner. In thisembodiment, spray chamber 325 is pressed against the seal plate 370 soas to form a seal using a sliding seal 330. Objective housing 305 isfitted with spray head 310 and is inserted into spray chamber 325 in asealed manner. Pump 380 is used to return fluid to the liquidtemperature conditioning system, such as a chiller 350, and can also beused to control the pressure inside the chamber interior 335, typicallyat about 1 atm. It should be understood that the desired spray chamberpressure can be calculated according to the characteristics of thecooling fluid used and the boiling point desired (in a givenembodiment).

Pump 365 is used to pump coolant through supply piping 395 to beinjected onto the DUT via atomizer banks 315. In one embodiment of theinvention, coolant is sprayed onto the stimulated DUT 360, whereupon itis heated to its boiling point and then evaporates and vapor forms inthe interior 335. The vapor may then condense on the chamber 325 walls,and is drained through channels 355, back into the pump 380. The vapormay also be directly fed into the chiller 350, although the load on thechiller will be increased. In another embodiment, the coolant simplyabsorbs the heat from the DUT without evaporating, whereupon theunevaporated liquid is returned to the liquid temperature conditioningsystem. While two thermal management scenarios have been presented,those skilled in the art can appreciate the fact that the relativecooling strengths of the fluid heat absorption and the evaporation maybe adjusted, for example, by choosing different fluids, nozzle designand number, fluid flow rate, fluid temperature, and chamber pressure asdescribed above.

The fluid may then be circulated through the liquid temperatureconditioning system 350 before being sprayed again onto the DUT. Thecoolant used in this embodiment is of high vapor pressure, e.g.,hydrofluoroethers or perfluorocarbons. Consequently, such fluidsevaporate readily when exposed to atmospheric condition. Therefore, asshown in this embodiment, the entire cooling system forms a closed loopsystem. The closed system may be vented through the solenoid valve 385,which may also be operated in conjunction with a vapor recovery systemsuch as a reflux condenser to mitigate additional vapor loss. For thispurpose, the liquid temperature conditioning system 350 comprises asealed chiller reservoir 390, capable of operating at both high and lowpressures, i.e., 10 psi above atmospheric pressure or a full vacuum of−1 atm. The reservoir 390 may also include a fluid agitation system (notshown) to enhance heat transfer from the coolant to the chiller coils(not shown). In this example, the chiller 350 and reservoir 390 arecapable of operating at low temperatures of down to, for example, −80°C.

Using this system, the temperature of the DUT can be varied so as to betested under various operating conditions. For example, the operator mayinput a certain operating temperature for testing the DUT. In oneembodiment, the actual temperature of the DUT can be detected by the ATE(not shown) in a manner known to those skilled in the art. For example,a temperature diode may be embedded in the DUT, and its signal sent tothe ATE. This is conventionally done for safety reasons such as, forexample, to shut the system if the DUT gets too hot. However, accordingto this embodiment of the invention, the temperature of the DUT is sentfrom the ATE to the controller 300. Using the actual DUT temperature,the controller 300 adjusts the cooling rate so as to operate the DUT atthe temperature selected by the operator. To control the cooling rate,the controller 300 may adjust, for example, the flow rate of coolant,the temperature of the coolant, or change the pressure in the chamber soas to change the boiling point of the cooling liquid.

As shown in FIGS. 2 and 3, and as alluded to above, various sensors andinstrumentation may be used to control the operation of the inventivecooling system. A pressure transducer 320 measures the coolant deliverypressure so as to control the pump 365 speed. Additionally, a pressuretransducer 322 measures the pressure inside the spray chamber so as tocontrol a solenoid valve 385 to obtain the appropriate coolant boilingpoint inside the spray chamber. Temperature sensor 340 is used tomeasure the coolant temperature close to the point of delivery, whilethe vapor temperature in the spray chamber is measured with temperaturesensor 345. Notably, from the spray chamber pressure and the vaportemperature (or coolant at its saturation temperature), it is possibleto determine the thermodynamic state of the coolant delivered to thestimulated DUT. A mechanical pressure relief valve 326 provides a safetyrelease in the event that the solenoid valve 385 fails.

In the embodiments of FIGS. 2 and 3, the effects of the atomized coolanton imaging needs to be minimized. One way to do this is by using theoptional shield 302, so as to prevent the mist from entering the opticalaxis of the imaging system. In this manner, when the objective housingis moved in to image a particular area on the DUT, the shield can bemade to touch, or to be very close, to the DUT so as to shield that areaof the DUT from the mist. On the other hand, if one wishes to avoid theuse of the shield, then the spray needs to be adjusted to enable bestimaging under the wavelength of the light being used. That is, thedroplet size of the mist needs to be controlled depending on theoperation of the microscope. For example, imaging may be done using, forexample, white light, or emission may be detected using, for example,infrared light. These different wavelengths would result in better imageby appropriate selection of the droplet size of the mist. This can beselected beforehand, or by the operator during testing.

On the other hand, in a further aspect of the invention, an improvedimaging is obtained using a solid immersion lens (SIL) in combinationwith the objective lens. The SIL enables transmission of optical energybetween the DUT and the objective lens practically regardless of thetype and manner of cooling spray used. Thus, the atomizers and the fluidpressure can be selected for optimal heat removal efficiency.

Solid immersion lenses (SIL) are well known in the art and are describedin, for example, U.S. Pat. Nos. 5,004,307, 5,208,648, and 5,282,088,which are incorporated herein by reference. FIG. 4 depicts an embodimentof the cooling system of the invention used in conjunction with a SIL.As exemplified in FIG. 4 many of the elements of this embodiment aresimilar to those of the embodiments of FIGS. 2 and 3. However, in thisembodiment, a SIL 450 is affixed to the tip of the objective housing405. In operation, the STE, 450 is “coupled” to the DUT, so as to allowcommunication of evanescent wave energy. In other words, the SIL iscoupled to the DUT so that it captures rays propagating in the DUT atangles higher than the critical angle (the critical angle is that atwhich total internal reflection occurs). As is known in the art, thecoupling can be achieved by, for example, physical contact with theimaged object, very close placement (up to about 20-200 micrometers)from the object, or the use of index matching material or fluid. Inaddition to increasing the efficiency of light collection, the use ofSIL 450 also prevents, or dramatically reduces, any deleterious effectsof the mist on the image because the mist cannot intervene between theSIL and the DUT.

In the embodiment of FIG. 2, two banks of atomizers are used. On theother hand, in the embodiment of FIG. 4, four banks of atomizers areused. It should be appreciated, however, that the number of atomizersand the number of banks of atomizers are provided only as examples, andother numbers and arrangements may be used. For example, the atomizersmay be placed in a circular arrangement about the objective housing,rather than in linear banks. Similarly, the atomizers may be attacheddirectly to any optical receiver used, e.g., objective lens housing,rather than placed in a spray head. Furthermore, various injectors maybe operated at different spray rates or be provided with differentcooling fluid, or same cooling fluid, but at different temperature.Optionally, different spray heads may be adjusted to provide spray atdifferent angles.

In the embodiments described above, a conventional tester head adapteris used to mount the DUT. An exemplary arrangement of mounting the DUTis depicted in FIG. 5. The DUT 560 is mounted onto the DUT board 590 andheld in place by retention frame 570. To prevent fluid from reaching theelectrical contacts of the DUT, an o-ring seal 510 is located betweenthe DUT retention frame 570 and the DUT carrier 565. In addition, ano-ring seal 520 is provided between the DUT retention frame 570 and theseal plate 580. In this manner, non-dielectric coolants such as watermay be used without altering the electrical behavior of the DUT becausethe non-dielectric coolant does not come in contact with the electricalpins.

FIG. 6 depicts another embodiment of a cooling system of the invention.In this embodiment, the electrical pin side of the DUT is being cooled,i.e., backside cooling. In this embodiment, a fluid coupler 615 isprovided on the integrated seal plate 680, enabling connection to asource of cooling fluid. Channel 610 is provided in the integrated sealplate 680 (now shown to incorporate the DUT retention frame 670),enabling the input fluid to reach the space 625 and get to the DUT'selectrical pins, i.e., enabling heat removal from the pin side of theDUT. An o-ring sealer 620 is provided to avoid fluid flow in betweenseal plate 680 and OUT board 690. Various options are demonstrated forremoval of the fluid from the space 625. One example is using outputchannel 630 to pump the fluid and output it to the chiller via coupler635. This option enables operation of this cooling system independentlyof any other cooling system provided. A second example is to provide anoutput port 640. Output port 640 can be used to output the fluid into aspray chamber, such as any of FIGS. 2-4. In this manner, a singlechiller may be used for both cooling systems. Of course, both examplesmay be used concurrently.

A further embodiment of the inventive spray cooling system is depictedin FIG. 7. The DUT 760 is held against the socket 762 by the retentionframe 761. In this particular example, the retention frame 761 isseparate from the seal plate 770, but as shown in other embodimentsherein, these two parts can be made as a single unit. Also, an optionalseal 766 is provided between seal plate 770, socket 762, and DUT board763. This ensures that no vapor will escape in the space between theseparts.

The spray chamber 725 is held against the seal plate 770 so that seal730 makes a seal with the seal plate 770. Atomizer banks 715 areprovided about objective housing 705. The condition inside chamberinterior 735 is monitored using pressure transducer 722 and temperaturesensor 745. The pressure inside chamber interior 735 is controlled usingsolenoid valve 785. Additionally, a mechanical pressure relief valve 726is provided for safety.

Cooling fluid is provided to the atomizer banks 715 using supply pump765. The pressure of the delivered fluid is measured by pressuretransducer 720, and the temperature is measured by temperature sensor740. After being sprayed, the fluid is collected and is pumped back tochiller reservoir 790 using return pump 780. The fluid level inside thechiller is monitored by level sensor 796, which can also be used as anadded variable for thermal management control, while the pressure insidethe chiller is monitored by pressure transducer 791. A mechanicalpressure relief valve 792 is provided for safety. The temperature of thefluid inside the chiller is controlled using chiller coils 793 andheater 794. As shown, all the sensors, actuators, and pumps areconnected to computer/controller 700.

As is known, in order to inspect the DUT, it is customary to thin theDUT. Consequently, when devices generate heat, the heat does not spreadwell over the entire DUT and a localized heat spot is created. If spraycooling is used to spray directly onto the DUT, the spray mayimmediately evaporate and create a gaseous layer over the localized heatspot thereby preventing further spray from reaching and cooling thatspot. To avoid that, in the embodiment of FIG. 7 a transparent coolingplate 764 is provided over the DUT 760, so as to enhance spreading ofheat from localized heat spots. The spray is then applied on the coolingplate, which may be made from, for example, silicon, sapphire, ordiamond.

FIG. 8 is a cross section schematic of a DUT holder arrangement withseparate DUT retention frame 870 and seal plate 880. The DUT 860 is heldagainst socket 885 by retention frame 870. An o-ring 820 is providedbetween DUT board 890, socket 885, and seal plate 880. Note that in thisschematic DUT 860 is depicted as substrate 860 and encapsulation 865.Also, the optional transparent cooling plate 874 is depicted coveringthe DUT 860. The transparent cooling plate 874 may be sealed to theretention frame 870 by, for example, indium or epoxy bonding, siliconsealant, and the likes.

FIG. 9 is a cross section schematic of a DUT holder arrangement withintegrated DUT retention frame and seal plate 970, and employingindependent backside cooling. That is, in this embodiment, the backsidecooling is independent of the spray cooling, so that different fluid ordifferent fluid temperature can be used for the backside cooling.Notably, in this arrangement, an o-ring seal 975 is provided between theDUT carrier 965 and the integrated seal plate 970. Another o-ring seal920 is provided between the DUT board 990, socket 985, and integratedseal plate 970. One or more channels 980 are provided in integrated sealplate 970 to provide cooling fluid to the backside of the DUT 960.Similarly, one or more channels 982 are provided in seal plate 970 toremove cooling fluid from the backside of the DUT.

FIG. 10 is a cross section schematic of a DUT holder arrangement withintegrated DUT retention frame and seal plate 1070, and employingbackside cooling. The DUT 1060 is held against the socket 1085 byintegrated retention frame/seal plate 1070. An o-ring seal is providedbetween the DUT board 1090, socket 1085, and seal plate 1070. One ormore channels 1080 are provided in seal plate 1070 so as to providecooling fluid to the backside of the DUT 1060. Similarly, one or morechannels 1082 are provided in seal plate 1070 so as to remove coolingfluid from the backside of DUT 1060. As shown by the arrows in FIG. 10,since no seal is provided between the DUT carrier 1065 and seal plate1070, cooling fluid may be drained in the space between the DUT carrier1065 and the seal plate 1070.

In all of the embodiments discussed above, a retention frame is used tosecure the DUT in the socket. As has already been discussed, for any ofthese embodiments the retention frame may either be a separatecomponent, as shown in FIGS. 5 and 8, or it may be integrated with theDUT seal plate, as shown in FIGS. 6, 9 and 10.

While the invention has been described with reference to particularembodiments thereof, it is not limited to those embodiments.Specifically, various variations and modifications may be implemented bythose of ordinary skill in the art without departing from theinvention's spirit and scope, as defined by the appended claims.Additionally, all of the above-cited prior art references areincorporated herein by reference.

The invention claimed is:
 1. A method for testing of a device under test(DUT) using an optical system, the method comprising: mounting the DUTonto a test bench; mounting a DUT retention frame with a seal plateabout the DUT; coupling a cooling head to the seal plate; electricallycoupling the DUT to a tester; providing a test signal from the tester tothe DUT; providing cooling fluid to the cooling head so as to spray atleast a portion of the DUT with the cooling fluid to control thetemperature of the DUT while using a shield to prevent mist fromentering optical axis of the optical system; and collecting light fromthe DUT using optical system.
 2. The method of claim 1, wherein saidcollecting light comprises coupling an imaging system to said DUT andpreventing said cooling fluid from entering an optical axis of theimaging system.
 3. The method of claim 1, wherein said collecting lightcomprises contacting said DUT with a solid immersion lens (SIL) andproviding a shield about said SIL.
 4. The method of claim 1, whereinspraying comprises applying the cooling fluid to a plurality of nozzles.5. The method of claim 1, wherein spraying comprises applying thecooling fluid to a plurality of atomizers.
 6. The method of claim 1,wherein the spraying is designed to cause at least part of the coolingfluid to evaporate upon contacting the DUT.
 7. The method of claim 1,wherein collecting light from the IC comprises detecting opticalemissions caused by the response of the DUT to the test signal.
 8. Themethod of claim 1, further comprising preventing the cooling fluid fromreaching contact pins of the DUT.
 9. The method of claim 1, furthercomprising enabling cooling of the DUT from a contact pin side byallowing cooling liquid to reach the contact pins of the DUT.
 10. Themethod of claim 9, wherein allowing cooling liquid to reach the contactpins of the DUT comprises applying hydrofluoroether of perfluorocarboncooling liquid to the contact pins of the DUT.
 11. The method of claim9, wherein allowing cooling liquid to reach the contact pins of the DUTcomprises allowing the cooling fluid to reach the contact pins of theDUT.
 12. The method of claim 1, further comprising applying an NIRtransparent cover plate to the DUT.
 13. The method of claim 1, furthercomprising affixing the cooling head to a translation stage.
 14. Themethod of claim 1, wherein mounting a DUT retention frame with a sealplate about the DUT comprises forming a hermetic seal between thecooling head and the seal plate.
 15. The method of claim 1, whereinmounting a DUT retention frame with a seal plate about the DUT comprisesforming a non-hermetic seal between the cooling head and the seal plate.16. The method of claim 1, further comprising arranging a plurality ofnozzles in the cooling head.
 17. The method of claim 16, whereinarranging a plurality of nozzles comprises dividing the plurality ofnozzles to a plurality of banks.
 18. The method of claim 16, whereinarranging a plurality of nozzles comprises arranging the nozzlescircularly about the optical system.
 19. The method of claim 17, furthercomprising applying the cooling fluid to the plurality of banks, whereinat least one of the banks receives the cooling fluid at one of:different flow rate, different cooling fluid, or different temperature.